The invention is directed to a sickleless internal gear pump for generating high pressure.
Internal gear pumps of a type known, e.g., from DE 41 04 397 A1 generally have an internal ring gear with which meshes an external pinion in driving fashion. The pinion has one tooth less than the ring gear and is arranged eccentric to the ring gear in such a way that always the outside of a tooth head on the pinion to contact the inside of a tooth head on the ring gear. Gear pumps of this type additionally have a suction port in the area in which the teeth disengage as the pinion rotates. Analogously, they feature a pressure port on the side opposite the suction port, where the teeth mesh again. This assures the feeding of pressure medium into or out of the interior of the ring gear, through essentially radial apertures. These apertures originate from the shell surface of the ring gear and empty in its tooth bottom.
The circumference of the ring gear divides thus into a suction space, in which the pressure medium is by the suction port sucked through the apertures, and in a pressure space, in which the pressure medium is through the apertures forced outward from the interior of the ring gear. These two areas are in the tooth engagement separated by the so-called dead center of the toothing.
On the sickleless internal gear pump known from DE 41 04 397 A1, the flank seal of a pinion tooth with the relevant ring gear tooth ends, due to the small number of teeth, far before dead center of the toothing. The area from the limit point of the flank seal up to dead center is part of the pressure space in which, thus, pressure medium is being pumped. This residual quantity of pressure medium also should be pumped into the pressure space, since otherwise the specific delivered volume diminishes appreciably. (Compare to theoretical q).
The missing seal on the tooth flank results in a deterioration of the volumetric efficiency. What is needed in the art is a sickleless internal gear pump with involute teeth (i.e., with a large angle of engagement in operation), with which the theoretical, specific delivery volume is being pumped without encountering volumetric efficiency losses.